There are many micro actuators (hereinafter referred to as actuators) which are in a research-and-development stage, but the number of actuators which have reached the product stage is very small. This is conceivably due partly to the difficulty in the microminiturization of the actuators themselves. In such a situation, Japanese Patent Unexamined Publication No. Hei. 8-90477 is known as the conventional art of the actuator which discloses the basic configuration of a product.
Such an actuator is characterized by a drive mechanism in which the expanding and contracting displacement of a movable frame due to a piezoelectric element is converted to the opening and closing displacement of a U-shaped pair of gripper fingers through a swinging mechanism consisting of a hinge and levers, and there is an advantage in that the pair of gripper fingers exhibits equalized opening and closing behavior with respect to an object to be gripped.
With the above-described conventional actuator, however, to utilize the expanding and contracting displacement of the piezoelectric element as the displacement for actuating the gripper, a mechanism for enlarging the displacement must be provided, so that the structure has been complex. For example, since the expanding and contracting displacement of the piezoelectric element is on the order of nanometers, there has been a problem in that a mechanism for enlargement by a factor of several hundreds is required to obtain an opening and closing displacement of even several hundred microns for the gripper fingers.